A conventional electret condenser microphone has a frame affixed with a vibratory diaphragm and a backplate disposed substantially parallel to the diaphragm with a predetermined space reserved therebetween, as disclosed in Japanese Unexamined Patent Publication No. 2000-050393 and Japanese Unexamined Patent Publication No. 2004-222091.
The frame and the backplate have substantially the same outer diameters and are vertically stacked one on top of the other. This structure is a bottleneck in reducing the thickness of the conventional electret condenser microphone.